Gonarthrosis is a disorder in which wear of cartilage which functions as a cushion of the knee joint causes inflammation or deformation of the knee joint, resulting in pain. The number of patients suffering gonarthrosis increases with age. However, if the thickness and surface shape of the cartilage of the femur can be accurately known before the condition reaches a crisis, a preventive action can be taken. With the population increase of the elderly, the number of gonarthrosis patients is currently expected to increase, and a simple diagnosis method is desired.
Known methods of diagnosing gonarthrosis include a method in which an arthroscope (endoscope) is inserted into the knee and a state of the surface of the cartilage is observed, and a method in which gonarthrosis is estimated based on the degree of opening of a gap in the joint through X-ray examination. However, these diagnosis methods cannot measure the thickness of the cartilage or obtain a three-dimensional shape of the cartilage.
In consideration of this, Patent Literature 1 discloses a system wherein an in-joint probe is inserted into the knee joint and ultrasound is transmitted and received, to evaluate the thickness of the cartilage of the knee joint. However, because this system is invasive, the system cannot be easily used. Therefore, this system is not suited for examination of many examinees such as a periodical medical examination.
An MRI (Magnetic Resonance Imaging) device is a non-invasive image diagnosis device, can in principle image the cartilage distinguished from the bone, muscle, body fluids, etc., and can measure the thickness of the cartilage. However, the usage cost for MRI is high and the measurement requires a long time, and thus, the MRI is not suited for use in examination of many examinees.